Hydraulic systems are often used to control the operation of hydraulic actuators of work machines. These hydraulic circuits typically include valves that are fluidly connected between the actuator and a pump and valves that are fluidly connected between the actuator and a reservoir. The valves control a flow rate and direction of pressurized fluid to and from chambers of the actuator to create pressure differentials within the actuator to affect movement thereof. Often, one or more of these valves are controlled in response to the pressure of the pressurized fluid within a portion of the hydraulic system and/or an associated chamber of the hydraulic actuator to reduce lag time between changing operational demands and valve actuation. Pressures within the hydraulic systems and, in particular, within chambers of the hydraulic actuators, however, may oscillate rapidly causing the valves to have overactive displacements which may lead to valve instability and/or premature wear.
A method of operating a hydraulic actuator is described in U.S. Pat. No. 6,467,264 B1 (“the '264 patent”) issued to Stephenson et al. The '264 patent discloses a pair of supply valves to direct fluid from a pump to respective head-end and rod-end chambers of a piston-cylinder arrangement. The '264 patent also discloses a pair of drain valves to direct fluid from respective head-end and rod-end chambers of the piston-cylinder arrangement to a reservoir. Each of the head-end and rod-end valves are proportional valves actuated by solenoids to selectively allow fluid to and/or from the piston-cylinder arrangement. The '264 patent further discloses a metering valve to control the pressure drop across the drain valves to improve the accuracy of the flow of fluid to the reservoir.
Although the metering valve of the '264 patent may control the pressure drop across a drain valve directing fluid from the piston-cylinder arrangement to the reservoir, it may not increase stability of the drain valve by reducing overactive displacements.
The present disclosure is directed to overcoming one or more of the problems set forth above.